蛋白营养对工业养殖大菱鲆(Scophthatmus maximus L.)幼鱼生长、氨氮排泄及肌肉氨基酸的效应

Effects of the Protein Level on the Growth, Ammonia-Nitrogen Excretion, and Amino Acid Accumulation in the Muscle of Industrially-Cultured Juvenile Turbot (Scophthatmus maximus L.)

中文关键词: 蛋白质  生长  氨氮排泄  肌肉氨基酸  大菱鲆  封闭循环水

英文关键词: Protein  Growth  Ammonia nitrogen excretion  Muscle amino acids  Turbot (Scophthatmus maximus L.)  Recirculating aquaculture systems

中文摘要:

      在封闭循环水养殖条件下，选用体重为(145.08±0.56) g大菱鲆(Scophthatmus maximus L.)幼鱼，进行4种饲粮蛋白质水平(41%、46%、50%和55%，即Ⅰ、Ⅱ、Ⅲ和Ⅳ组)的单因素实验74 d，研究蛋白营养变化对工业养殖大菱鲆幼鱼生长、氨氮排泄及肌肉氨基酸的影响。结果显示：(1) 实验鱼增重率的提高随饲粮蛋白含量升高先快后慢，Ⅲ、Ⅳ组增重率极显著高于Ⅰ、Ⅱ组18.48%–65.95% (P<0.01)，Ⅲ、Ⅳ组间无显著差异；饲料系数则相应下降，Ⅲ、Ⅳ组分别极显著低于Ⅰ组25.64%、28.21% (P<0.01)，Ⅱ、Ⅲ、Ⅳ组间无显著差异；(2) 实验鱼氨氮排泄率与饲粮蛋白水平呈正相关，即随饲粮蛋白水平提高，实验鱼氨氮排泄率呈先缓增后趋平稳趋势，饲粮蛋白含量超过50%时，排泄率急剧上升。氨氮排泄率呈明显昼夜节律性，即摄食后排泄率逐渐升高，6–8 h达排泄高峰，后逐渐降低，以此周期性循环。早投喂后6 h各组排泄率达高峰，Ⅳ组极显著高于其他3组17.95%–35.07% (P<0.01)；晚投喂后8 h各组排泄率达1 d内第2次高峰，Ⅳ组极显著高于Ⅰ组31.27% (P<0.01)，显著高于Ⅱ组14.25% (P<0.05)；(3) 17种常见氨基酸在各处理组鱼肌肉内含量丰富，总量均高于65 mg/100 mg，且随饲粮蛋白含量升高呈渐增趋势，其中，Ⅲ、Ⅳ组无论肌肉氨基酸总量、必需氨基酸含量，还是鲜味氨基酸含量，均略高于Ⅰ、Ⅱ组，但4组间差异不显著(P>0.05)；饲粮蛋白含量变化对实验鱼肌肉氨基酸组成比例无显著影响。总之，饲粮蛋白水平过高，不能显著改善生长性能，却会显著提高氨氮排泄；同时，既不能改变肌肉氨基酸比例，也难以显著增加肌肉氨基酸积累。研究表明，大菱鲆幼鱼饲粮适宜蛋白质水平为45%–50%。

英文摘要:

      A study was conducted to investigate the effects of the dietary protein level on the growth, ammonia-nitrogen excretion, and amino acid accumulation in the muscle of juvenile turbot (Scophthatmus maximus L.) in a recirculating aquaculture system. One hundred and forty-four healthy juveniles with initial body weight of (145.08±0.56) g were randomly divided into four groups each of which had three replicates of 12 fish. Groups Ⅰ–Ⅳ were fed with diets containing 41%, 46%, 50%, and 55% protein respectively. The fishmeal content was the only variable in the diet. The results were shown as follows: (1) As the protein level went up, the weight gain rate (WGR) increased first rapidly and then slowly, while feed conversion rate (FCR) showed a reversed trend. The WGRs of Groups Ⅲ and Ⅳ were significantly higher than that of Groups Ⅰ and Ⅱ by 18.48%–65.95%, and compared to Group Ⅰ the FCRs of Groups Ⅲ and Ⅳ were lower by 25.64% and 28.21% respectively (P<0.01). (2) Ammonia excretion rate (AER) of juveniles cyclically varied between day and night, and there were two peaks appearing 6–8 h post feeding. There was a positive correlation between AER and the dietary protein level. The AER of Group Ⅳ was significantly higher than that of other groups by 17.95%–35.07% (6 h post feeding in the morning, P<0.01) and 14.25%–31.27% (8 h post feeding in the evening, P<0.05). The AER of juveniles increased sharply when the dietary protein level was above 50%. (3) The content of 17 amino acids in muscle was higher than 65 mg/100mg in each group, and it rose along with the increase in the dietary protein level (P>0.05). The contents of total amino acids, essential amino acids, and flavor amino acids in the muscle of Groups Ⅲ, Ⅳ were not significantly higher than those of other groups (P>0.05). There was no difference in the amino acid composition between groups (P>0.05). The results indicated that the growth performance of juveniles might not be improved when the dietary protein level was above 50% at which level the AER was markedly increased, and that the content and composition of amino acids in the muscle might not be altered by the dietary protein level. Therefore, the optimal protein level of juvenile turbots may be 45%–50%.